Cadence-Kids is an R21 exploratory/developmental study designed to 1) measure and link cadence (steps/minute) to intensity cut points across age in 6-20 year olds, and 2) describe children's and adolescents' behavior in free-living using these cut points. Cadence is just one of the temporal-spatial parameters of gait. Cadence multiplied by stride length equals speed. Capture and expression of physical activity in terms of cadence represents an overlooked opportunity to examine free-living patterns of ambulatory intensity. To achieve our primary aim, we will identify and recruit 10 children and adolescents (5 boys, 5 girls) from each age-year between 6-20 years (a span of 10 age-years for a total of 150 children and adolescents) to a lab- based study of cadence (assessed on a treadmill) followed by a week-long free-living study of habitual physical activity. Under laboratory conditions we will calibrate different treadmill cadences with indirect calorimetry. We will subsequently monitor these same individuals' habitual minute-by-minute cadence for one week. We hypothesize that children's intensity will increase as cadence increases in a linear or nonlinear fashion such that we will be able to develop novel statistical models for predicting markers (cut points) of intensity from cadence. We further hypothesize that free-living estimates of children's time in at least moderate intensity activity will be higher using sex and age-calibrated cadence results compared to that obtained from more generic activity count cut points. We are uniquely positioned at the Pennington Biomedical Research Center to successfully conduct Cadence Kids as designed in a 2-year time period. We have established recruiting methods, excellent connections with schools and the community, and are fully experienced in exercise testing and accelerometry. The information derived from this R21 exploratory/developmental study will inform future R01 investigations related to cadence as an indicator of intensity in determining healthful levels of children's free-living physical activity. If successful, we expect that cadence cut points will be used both to assess ambulatory intensity, but also to inform program design focused on increasing not only the volume of physical activity (e.g., steps/day) but also its intensity (e.g., cadence) in user-friendly metrics.